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This sweet, jammy onion tart turns basic stuff you've got at home into a fancy starter that'll wow your dinner crowd. When those soft, caramelized onions meet the sharp kick of blue cheese, you get something that's cozy yet classy—just right for everything from big holiday bashes to laid-back wine evenings.
I whipped this tart up during a panic moment when friends were coming over and all I had were onions and cheese in my fridge. What started as a quick fix has turned into the thing everyone asks me to bring, and now it shows up at all my holiday get-togethers.
What You'll Need
- Extra virgin olive oil: Forms the base for slowly cooking down those onions until they're rich and flavorful
- Onions: Cut from top to bottom so they hold their shape while they transform into sweet, soft goodness
- Brown sugar: Helps speed up the browning process, making the onions naturally sweeter
- Balsamic vinegar: Adds depth and a slight tang that cuts through the sweetness nicely
- Frozen puff pastry: Gives you a flaky, buttery crust without any hassle of making dough
- Brie cheese: Turns all melty and gooey in the oven; always take off the white outside part for best results
- Gorgonzola cheese: Brings a zingy bite that works against the sweet onions; try to find a soft one that melts well
- Fresh tarragon: Adds a surprise licorice-like flavor that makes this tart special; look for bright green bunches
Easy Cooking Steps
- Get Those Onions Jammy:
- Warm olive oil in a big, deep skillet over medium-high heat till it's hot. Toss in your sliced onions and cook them for 10 minutes, giving them a stir now and then until they're soft and golden. Sprinkle the brown sugar over them, then add balsamic vinegar, salt, and pepper. Turn the heat down to medium-low and let them cook uncovered for 20-25 minutes, stirring once in a while until they're super soft and jam-like. If things look dry, splash in a bit of water to stop them burning. Take them off the heat and let them cool completely.
- Sort Out Your Dough:
- Heat your oven to 400°F with the rack in the middle. Unfold your thawed puff pastry onto a baking sheet lined with parchment. Roll it out to about 10-by-14 inches with a rolling pin. Poke holes all over the dough with a fork every couple inches so it doesn't puff up too much and stays crispy.
- Put It All Together:
- Spread your cooled onion mixture all over the pastry right to the edges. Scatter the chopped brie and gorgonzola evenly on top. Finish by sprinkling fresh tarragon leaves over everything.
- Bake It Up:
- Stick the tart in your hot oven for 18-20 minutes, turning the pan halfway. You'll know it's done when the edges are puffy and dark golden, and all the cheese has melted. Take it out and let it sit for 5 minutes before cutting it up.
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The tarragon in this tart is my little trick. I stumbled on it when my herb garden let me down one summer and I had to swap out thyme. Those slight licorice notes add something unexpected that leaves guests scratching their heads. My next-door neighbor actually refused to leave my kitchen once until I told her what made it taste so good.
Prep It Early
This tart is a lifesaver when you're hosting because you can do most of the work ahead. The onions can be cooked up to three days before and kept in the fridge in a sealed container. You can put the whole thing together and keep it unbaked in the fridge for up to 24 hours. Just add a couple minutes to the cooking time if it's coming straight from the cold. For surprise visitors, I always keep puff pastry in the freezer and jars of cooked onions in the fridge ready to go.
What To Serve With It
The deep, savory flavors in this tart need something bright alongside them. Try a fresh green salad with a simple lemon dressing. For drinks, go with something that has enough zip to cut through the richness—a crisp Sauvignon Blanc or Chardonnay without oak works great. If you're serving it as a starter, try cutting it into tiny two-inch squares and pop a small sprig of fresh tarragon on each for a fancy touch at cocktail parties.
Common Problems Solved
When you're working with puff pastry, getting the timing right matters a lot. Keep it in the fridge until you're totally ready to use it. If it gets too warm, it'll get sticky and hard to work with. If that happens, just put it back in the fridge for 15 minutes before trying again. For the crispiest bottom, bake the pricked dough by itself for 5 minutes before adding toppings, especially if you're making it for a big group. This keeps the middle crisp even when it sits out during a party.
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This caramelized onion tart wins friends and makes gatherings special with its knockout blend of sweet and savory tastes.
Frequently Asked Questions
- → Can I make this onion tart ahead of time?
You bet! The slow-cooked onions can be made up to 3 days early and kept in the fridge. You can also put the whole tart together and keep it in the fridge for a day before you bake it. Just cook it a few minutes longer if it's cold from the fridge.
- → What can I use instead of tarragon in this tart?
No tarragon around? Try fresh thyme, rosemary or basil instead. They'll each give a different taste, but they all go great with the sweet onions and cheese mix.
- → How should I serve this onion and cheese tart?
This tart works in so many ways! Cut it into small squares for a fancy starter, pair it with a green salad for a main dish, or eat it at room temp for picnics or brunches. It's also great as part of a cheese spread.
- → Can I swap out the cheeses in this tart?
For sure! While Gorgonzola and Brie make a great sharp and creamy combo, feel free to try other cheeses. Gruyère adds a nutty flavor, fontina melts beautifully, or try goat cheese for some tang. Just make sure you mix up the flavors.
- → Why should I poke the pastry with a fork?
Poking holes in the puff pastry stops big air bubbles from forming while it bakes. This gives you a flat surface for your toppings and helps the pastry cook evenly throughout.
- → How do I know when my onions are cooked right?
Well-cooked onions should look golden brown but not burnt. They'll feel super soft and shrink down quite a bit. They'll taste sweet and rich without any sharp oniony bite. Don't rush it though, good onions need about 25-30 minutes of slow cooking.